Adjustable voltage supply



Aug. 29., 1967 B. E. DENTON ADJUSTABLE VOLTAGE SUPPLY Filed June l0, 1964 3,339,103 ADJUSTABLE VOLTAGE SUPPLY B'ethel E. Denton, Robards, Ky., assgnor to Radio Corporation of America, a corporation of Delaware Filed June 10, 1964, Ser. No. 373,992 4 Claims. (Cl. 315-31) ABSTRACT GF THE DISCLOSURE A three-winding arrangement, with common adjustable core, supplies a variable amplitude, variable polarity pulse to output electrode of a rectifier to buck or aid, to a selectable degree, a larger, fixed-amplitude pulse input to the rectifier. One outside winding and a segment only of the other outside winding, series-connected across smaller, fixed amplitude input pulse source, form an adjustable inductive voltage divider. Middle winding is connected to divider winding junction, and induced middle winding voltage adds to or subtracts from divider output, depending upon core position. Remaining outside winding segment is interposed in connection between divider output and middle winding to provide additional variable pulse component, expanding adjustment range. Embodiments for range expansion at either high or low end are disclosed.

This invention relates generally to adjustable voltage supplies, and particularly to an improved form of such supplies suitable for service in supplying an adjustable voltage to the focus electrode structure of a cathode ray tube.

In U.S. Patent No. 3,113,237, issued on Dec. 3, 1963, to James C. Schopp and Leonhard E. Annus, an adjustable focus voltage supply for a tri-gun, shadow mask color kinescope is disclosed. In the arrangement of the Schopp et al. patent, the focus electrodes of the tri-gun tube are supplied in common with a unidirectional voltage derived by rectification of fiyback pulses developed in the horizontal defiection output transformer associated with energization of the tubes deflection yoke. The rectifier of the supply receives two pulse inputs: (a) a relatively large, fixed amplitude pulse of positive polarity is supplied to the rectifier input electrode; (b) a relatively smaller pulse of variable amplitude and selectable polarity is applied to the rectifier output electrode. Selection of the polarity of the latter pulse determines whether the output voltage of the supply will correspond to the voltage level of the fixed pulse augmented by an added incremental voltage or lessened by an effectively subtracted incremental voltage; variation in the pulse amplitude controls the amount of augmentation or lessening.

The Schopp et al. patent discloses an arrangement of inductances for use in development of the above-discussed variable amplitude, variable polarity pulse. In the dis- United States Patent O closed inductance arrangement, a first and a second winding are connected in series across the additional pair of fixed terminals on the transformer. Both of these fixed terminals are relatively low voltage terminals thereof, and the amplitude of the fiyback pulse appearing between these terminals is of an order of voltage corresponding to approximately half the width of the desired range of focus voltage adjustment. The pulse output terminal of the inductance arrangement, at which appears the variable amplitude, variable polarity pulse for delivery to the focus rectifier output electrode, is coupled via a third winding to the junction of the first and second windings. A common, adjustable magnetic core is associated with the first, second and third windings, and serves both (a) to diierentially vary the inductances of the first and second windings, and (b) to simultaneously differentially 3,339,103 Patented Aug. 29, 1967 v effect on the nature of the pulse appearing at the pulse output terminal of the inductance arrangement. In the first place, it controls the effect of the first and second windings as an inductance divider of the pulse voltage appearing between the pair of fixed terminals of the transformer. That is, in one extreme of core adjustment, the inductance ratio of the first and second windings is such as to provide a pulse voltage at their junction point of maximum amplitude, approaching the amplitude of the pulse appearing between the fixed transformer terminals; in the other extreme of core adjustment, the amplitude of the pulse voltage appearing at the winding junction point is at a minimum, approaching zero amplitude, the inductance ratio of the first and second windings being inverted. Additionally, however, adjustment of the core differentially varies the degree of coupling between the third winding and each of the second and first windings. These couplings are oppositely poled, whereby in one extreme of core adjustment, the pulse voltage developed across the third winding will be of one polarity, v

whereas at the other extreme of core adjustment, the pulse voltage developed thereacross will be of the opposite polarity. The pulse voltage appearing at the pulse output terminal of the inductance arrangement is the summation of (a) the pulse voltage appearing at the junction of the first and second windings, and (b) the pulse voltage developed across the third winding.

The present invention is directed to a modification of the above-des-cribed focus supply arrangement of the Schopp et al. patent, the modification providing improved performance in that a wider range of focus voltage adjustment may be obtained without requiring higher levels of input pulse amplitude. This performance improvement is obtained through use of the present invention without loss of the many practical advantages inhering in the general approach of the Schopp et al. patent. Thus, desirable regulation properties for the supply are obtained without requiring the use of such power consuming components as resistive potentiometers. High step-up ratios leading to undesired ringing effects are avoided. The inductances employed are subjected onlyto relatively low voltages, whereby they may take an inexpensive form. f

The expanded focus voltage adjustment range provided by the present invention is obtained in a manner compatible with obtaining pulse inputs for the supply at tapping points on the output transformer convenient for other pulse utilizations as well.

In accordance with the principles of the present invention, the above-noted adjustment range expansion is realized by modification of the Schopp et al. winding arrangement in the following manner: One of the first and second windings (i.e., one of those associated with the inductance divider function) is provided a greater inductance value than the other, as by providing it, for

example, with a greater number of turns than the other.

. nected between the intermediate tapping point and one end of the third winding, while the opposite end of the third winding is coupled to the output electrode of the focus rectifier.

As a result of the described winding connections, a segment of the tapped winding is included in series with the third winding in the coupling from the junction of first and second windings to the rectifier output electrode. Accordingly, the pulse supplied to the rectifier output electrode corresponds to the algebraic sum of three contributions: (1) the divided pulse voltage developed at the junction; (2) the pulse voltage developed across the additional segment of the tapped winding due to inductive coupling between the two segments of the tapped winding; and (3) the pulse voltage developed across the third winding as the resultant of the oppositely poled inductive couplings between it and the first and second windings.

At the adjustment range extreme at which the divider portion of the tapped winding exhibits a low inductance value (and thus has only a relatively small pulse voltage developed across it), contribution (2) from the additional segment is minimum; at the opposite 4adjustment range extreme, contribution (2) has a maximum value. Depending upon the choice of which of the first and second windings is to be the tapped winding (i.e., depending upon the location of the tapped winding in the circuit), the adjustment range expansion represented by the addition of contribution (2) may be provided at either the high or low end of the focus voltage range.

Accordingly, it is a primary object of the present invention to provide a novel adjustable voltage supply providing a wide range of adjustment of a relatively high voltage, with the adjusting components subjected only to relatively low voltages.

A further object of the present invention is to provide an improved focus voltage supply for a color kinescope which utilizes an arrangement of relatively inexpensive components to provide a wide range of focus voltage adjustment.

Other objects and advantages of the present invention will be appreciated by those skilled in the art after a reading of the following detailed description and an inspection of the accompanying drawing the single figure of which illustrates in block and schematic form a color television receiver incorporating a focus voltage supply in accordance with an embodiment of the present invention.

The color television receiver illustrated in the drawing is of a general form exemplified by the RCA color television receiver chassis No. CTC-l5. The receiver is illustrated mainly in block form, with, however, details of the horizontal output circuitry and associated voltage supplies shown schematically.

Conventional television signal receiver apparatus 11 serves to process carrier waves modulated by a composite color television signal. The apparatus 11 incorporates such conventional elements as a tuner, IF amplifier, video detector, etc. The video frequency signals recovered from the modulated carrier in the receiver apparatus 11 are amplified in a video amplifier 13 for application to a chrominance channel 15, a luminance channel 17 and deflection sync separator apparatus 19.

The chrominance channel 15 may include, inter alia, the usual bandpass amplifier for selectively amplifying the modulated color subcarrier component of the receiver composite signal, color demodulation apparatus for synchronously detecting the color subcarrier at subcarrier phases appropriate to recovery of particular color difference signal information, and matrixing apparatus for processing the recovered color difference signals to forms suitable for application to a color image reproducer.

A three-gun, shadow-mask, color kinescope 20 serves as the color image reproducer of the illustrated receiver. The target assembly of the color kinescope 20 comprises a phosphor screen composed of a regular array of red-, greenand blue-emitting phosphor dots and an associated perforated mask. The color kinescope incorporates a trio of electron guns for respective excitation of the three differently colored phosphor dot arrays, each gun including a cathode, control grid, screen grid and focusing electrodes. The respective red, green and blue cathodes are designated 21R, 21G and 21B; the respective red, green and blue control grids are designated 23R, 23G and 23B; the respective red, green and blue screen electrodes are designated 25R, 25G and 25B; and the individual focus electrodes are electrically interconnected to provide a common focusing electrode structure designated 27. The color kinescope 20 also incorporates an ultor electrode (or final anode) 29.

Respective unidirectional operating potentials for the focusing electrode structure 27 and -for the ultor electrode 29 are provided at respective terminals FT and U; the manner in which these potentials are developed will be subsequently described. The individual screen electrodes 25R, 25G and 25B of the color kinescope 20 derive individually adjustable operating potentials from respective screen voltage adjusting potentiometers 31R, 31G and 31B, the latter being associated with particular DC voltage supplies also to be subsequently described.

The individual control grid electrodes 23R, 23G and 23B of color kinescope 20 receive respective red, green and blue color-difference signals from the respective output terminals CB, CG and CR of the chrominance channel 15. The respective cathodes 21R, 21G, and 21B of color kinescope 20 are individually connected to respective output terminals LR, LG and LB of the luminance channel 17, which processes the luminance component of the received composite signal and delivers such component in selectively different amplitudes to the respective output terminals LR, LG and LB.

Associated with the color kinescope 20 is a deflection yoke 41, responding to respective vertical and horizontal deflection waves to cause the color kinescope beams to trace a raster on the phosphor screen; also conventionally associated with the kinescope 20 is a convergence yoke (not illustrated) responding to suitable dynamic convergence waveforms to cause the color kinescope beams to properly converge in the target region throughout the scanning ofthe raster.

Outputs of the sync separator 19 are supplied to vertical deection circuits 43 and to horizontal defiection circuits 45. The vertical deflection circuits 43 generate a vertical deflection wave for application to the terminals V, V of the defiection yoke 41, under the control of vertical synchronizing pulses derived from the sync separator 19. Similarly the horizontal defiection circuits effect generation of the horizontal deection wave to be applied to the terminals H, H of the deflection yoke 41. However, in contrast with the vertical deflection circuit showing in block form only, a number of the details of the horizontal deection Wave output circuitry are shown schematically in the drawing.

The horizontal deflection circuits 45 include a horizontal output tube 47 (only partially shown). The output electrode, anode 49, of the horizontal output tube 47 is coupled to the horiozntal windings H, H of the deflection yoke 41 via horizontal output transformer 50, illustrated schematically in the drawing.

A direct current connection is provided between anode 49 and an intermediate terminal O of the transformer 50. The output of tube 47 is effectively developed across a primary winding section of the transformer 50, that primary winding section comprising the winding segments extending between intermediate terminal O and a low potential terminal L of the transformer. Illustratively, this primary winding section may in practice comprise a pair of windings wound together in bifilar fashion between terminals O and L, with taps at predetermined intervals along this winding length. As shown in FIGURE l, a tap I is provided at a particular point of relatively low voltage level for purposes to be subsequently described. At the level of this tapping point I, a dire-ct connection is provided between the two bifilar transformer windings.

At points on the primary winding section of higher voltage level than that at tapping point J, the bifilar windings are provided with respective tapping points C1 and C2. The horizontal yoke windings H, H are coupled between the low potential terminal L of transformer 50 and the adjustable arm of a potentiometer 52 (serving a raster centering adjustment purpose), the fixed terminals of which are directly connected to the transformer tapping points C1 and C2, respectively.

It will be seen from the foregoing circuit description that a form of step-down autotransformer coupling is thus provided between the horizontal output tube 47 and the horizontal windings of the yoke 41. The winding segments between terminals C2, C1 and terminal L serve as the secondary winding section in the step-down autotransformer circuitry.

An additional, tertiary winding section is provided for transformer 50 by winding segment extending from terminal O to a high potential terminal l. A diode rectifier 60 has its anode connected directly to the high potential terminal P of transformer 50; the cathode of diode 60 is directly connected to the energizing terminal U of the kinescopes ul-tor electrode 29. Diode 60 serves to rectify a -pulse input derived from terminal P for development of the relatively high unidirectional voltage required by the ultor electrode 29 for operation of the color kinescope 20. The pulse input to diode 60 is a stepped-up version of flyback pulses developed in the transformer primary windings during the retrace portion of the deflection cycle, when cutoff of the output tube 47 causes a sudden collapse of magnetic fields associated with these windings, leading to development of a relatively high amplitude voltage pulse at terminal O. In the circuit as described, the presence of the tertiary winding section O-P thus establishes a form of step-up autotransformer coupling between the output tube 47 and diode 60.

The conventional damper tube 63 is coupled across the secondary winding section of transformer 50, for operation in accordance with well-known reaction scanning and power recovery principles. In connection with the latter purpose, capacitors 67 and 69 are included in the damper tube circuit and the charge across these capacitors supplements the receivers conventional B-lsupply voltage (to which the anode of damper tube 63 is connected via the linearity adjusting inductor 65) to develop the so-called B-'boost voltage at terminal BB (directly linked to transformer terminal L).

The B-boost voltage at terminal BB is subject to -use at various points in the receiver. One of these points is associated with the voltage regulator tube 61. The regulator tube 61 provides a space discharge path that is coupled effectively in shunt with the color kinescope load on the high voltage rectifier 60. The purpose served by the regulator 61 is to ensure that the voltage delivered to the ultor terminal lU remains substantially constant despite the changes in the load represented by the kinescope that occur in operation of the receiver primarily due to variations in the DC content of the luminance signal drive. Should the kinescope current increase (tending to lower the ultor voltage), the current drawn by the regulator tube 61 correspondingly decreases so as to oppose the voltage variation tendency; conversely should the kinescope current decrease, the regulator current correspondingly increases.

Control of the regulator current in the desired manner is obtained by applying a sample of the B-boost voltage available at terminal BB to the control grid of regulator tube 61. The desired regulating effect is achieved Iby this technique due to the fact that the B-boost voltage tends to follow variations in the ultor voltage; whereby ncreases in the ultor voltage produce an increase in the regulator current, and Vice versa.

Also associated with the output transformer 50 is additional power supply circuitry, contributing to production of a so-called boosted-boost voltage, an augmented power supply voltage of an even higher level than the previously mentioned B-boost voltage. This boosted-boost circuitry includes the series combination of a diode 70 and a capacitor 71, this series combination being shunted across the transformer winding segment that extends between low potential terminal L and intermediate terminal J of the output transformer 50. Diode 70 rectifies the flyback pulse developed across this winding segment, developing a charge on the capacitor 71. The charge on capacitor 71 adds to the B-boost voltage appearing at the terminal L to provide a doubly-augmented power supply voltage at terminal Q, the junction of diode 70 cathode and capacitor 71.

One use for the boosted-boost potential developed at terminal Q is in energization of the screen grid electrodesVV 2ER, 25G and 25B or" color kinescope 20. The screen grid potential adjusting potentiometers 31R, 31B and 31G permit adjustment of the respectively associated kinescope screen grid potentials in a range intermediate the receivers B-llevel and the higher level of the boosted-'boost voltage. For this purpose one fixed terminal of each of the potentiometers is connected via a common dropping resistor 35 to the B+ supply of the receiver, while the other fixed terminal of each potentiometer is connected via a common dropping resistor 73 to the boosted-boost terminal Q. A ripple-reducing filter capacitor 75 is coupled between the latter fixed terminals and the B+ supply. Bypass capacitors 33R, 33G and 33B are coupled between the respective movable arms of the potentiometers and the high potential fixed terminals thereof. Each movable arm is directly connected to the respectively associated kinescope screen grid.

An additional power supply is associated with the output transformer 50, and it is this additional supply with which the present invention is particularly concerned.

This is the adjustable focus voltage supply 80, which responds to pulse inputs derived from the transformer 50 for development of an adjustable unidirectional potential for delivery to the energizing terminal FT of the focusing electrode structure 27 of color kinescope 20.

The focus supply includes a rectifier, diode 81; the anode of diode 81 is connected to the intermediate terminal O of output transformer 50; its cathode is connected via a resistor 83 to chassis ground, and via a resistor 87 to the focus electrode energizing terminal FT. One input to rectifier 81 is thus a iiyback pulse of relatively fixed amplitude, i.e. the pulse developed at transformer terminal O.

The diode 81 receives, in addition to this -ixed amplitude pulse, an additional input pulse of adjustable amplitude. This adjustable amplitude pulse is supplied to the diode cathode from the output of an inductance arrangement 90 via a capacitor 85. The capacitor 85 serves a dual function: i.e., it is a coupling capacitor for the adjustable pulse input to the rectifier, and additionally serves as a filter capacitor for the DC output.

The inductance arrangement 90 comprises a trio of windings 91, 93 and 95, with which a common adjustable core 97 is associated.

Preferably, the three windings 91, 93 and 95 are wound on a common coil form (not shown); the core 97 is positioned within the common coil form, subject to longitudinal adjustment of its location. The windings are located on the coil form inthe order named; i.e., the winding 93 is in a position intermediate the locations of the windings 91 and 95.

In one extreme of core adjustment (i.e., the core position shown in solid line outline in the drawing), core 97 extends within coils 91 and 93, -but is withdrawn from coil 95; for discussion purposes, this will be referred to as the reference position of `core 97. In the opposite adjustment extreme (shown in dotted line outline), the core 97 extends within coils 93 and 95 but is withdrawn from coil 91.

The three coils 91, 93 and 95 are wound in the same direction on the common coil form. Coil 91 has a greater number of turns than coil 95, and is provided with an intermediate tap. Illustratively, the coil 91 has twice the number of turns of coil 95 (though preferably wound about a segment of the common coil form of axial length comparable to that encompassed by coil 95), and the intermediate tap thereon comprises a center tap.

The windings 91, 93 and 95 are connected in the focus Supply circuitry in the following manner. The start S1 of winding 91 is directly connected to the intermediate tap I on the primary winding section of transformer 50. The center tap M1 of winding 91 is directly connected to the finish F5 of coil 95. The start S5 of coil 95 is directly connected to the low potential terminal L of transformer 50. The finish F1 of coil 91 is directly connected to the start S3 of winding 93 (which is shunted by a damping resistor 99). The finish F3 of coil 93 serves as the output terminal of the inductance arrangement 90, and is coupled by capacitor 85 to the cathode of focus rectiier 81.

The pulse voltage appearing at center tap M1 (the junction of windings -91 and 95) is at a minimum at the reference core position and increases to a maximum at the opposite adjustment extreme', the polarity is positive throughout the range of adjustment. Such variation of pulse voltage amplitude is the result of inductance divider action. That is, the S1-M1 segment of coil 91 forms with coil 95 an adjustable inductance voltage divider. The described circuit connections place the S1-M1 winding segment in series with coil 95 across the I-L segment of the output transformer 50. A divided version of the voltage pulse developed across the I-L transformer winding segment appears at the junction of the coil 91 segment and coil 95.

The amplitude of the divided pulse voltage at the junction depends upon the relative inductance values of the two elements of the divider (i.e., the relative inductance values of coil 95 and the S1-M1 segment of coil 91), and these values depend upon the core position. When the core 97 extends throughout the length of the Sl-Ml segment of coil 91 and is withdrawn from coil 95, the coil 91 segment has a maximum inductance value, and the coil 95 has a -minimum inductance value; the reverse is true when the core is withdrawn from the core 91 segment.

In a representative example, the ratio of the coil 91 segment and coil 95 inductance values varies from 6.5 to 1 (at the reference position) to 1 to 6.5 (at the opposite adjustment extreme); a representative value for the arnplitude of the pulse voltage developed at terminal I is +450 volts. Under such representative circumstances, the pulse voltage at M1 varies from +60 volts to +390 volts as the core is moved away from the reference position to the opposite adjustment extreme.

A variable pulse voltage is also developed across the segment Fl-Ml of coil 91. This pulse voltage development is due to inductive coupling between the two segments of coil 91. Where the two segments of coil 91 are of essentially equal length, the amplitude of the pulse voltage developed across the Fl-Ml segment is substantially equal in amplitude to the pulse voltage appearing across the S1-M1 segment. However, due to the circuit connections, the polarity at F1 is opposite to the polarity of the previously described variable pulse voltage developed at terminal M1. Thus, for the assumed conditions, the pulse voltage across the winding segment F1-M1 varies from a 390 volt level in the reference position to a 60 volt level at the opposite extreme, with the polarity throughout the range of `adjustment being effectively opposite to that of the divided pulse voltage at M1.

A third component of variable pulse voltage is developed across the winding 93. This pulse voltage development is due to inductive coupling between this Winding and its neighbors, coil 91 and coil 95. By virtue of the coil arrangement and circuit connections, the coupling between coil 91 and coil 93, on the one hand, and the coupling between the coil 93 and the coil 95 on the other hand, are effectively oppositely poled. The coupling between coil 93 and coil 95 is so poled as to induce a pulse voltage of positive polarity; i.e., an induced pulse voltage of a polarity such that F3 is positive relative to S3. The opposite is true with regard to the coupling between coils 91 and 93.

In the reference position, with the core 97 extending through the neighboring coils 91 and 93, but withdrawn from coil 95, the coupling between coil 91 and coil 93 is maximum, while the coupling between coil 93 and coil 95 is minimum. Thus, in the reference position, the pulse voltage across winding 93 is of maximum negative value, while at the opposite adjustment extreme, the pulse voltage is of maximum positive value. At some point intermediate the extremes of the -adjustment range, the pulse voltages induced by the two oppositely poled couplings are equal and opposite, resulting in zero pulse voltage across winding 93. For the previously considered parameter values, this results in a value for the pulse voltage component developed across winding 93 that varies from -390 volts (terminal F3 relative to terminal S3) at the reference position to +390 volts at the opposite adjustment extreme.

The pulse voltage appearing at the output terminal F3 of the inductance arrangement 90, and therefrom supplied to the cathode of rectifier 81, will be recognized as comprising the sum of three components: (a) the divided pulse voltage developed at terminal M1; (b) the pulse voltage developed across the Fl-Ml segment of coil 91; and (c) the pulse voltage induced across winding 93. For the described parameters, the variation of the resultant pulse voltage is from a -720 volt level at the reference position to a +720 volt level at the opposite -adjustment extreme; i.e., inductance larrangement operates upon a 450 volt pulse input to provide a pulse voltage output that Varies lover a range having a total width equal to approximately three times the magnitude of the pulse input, with polarity inversion in the middle of the range.

The effect of supplying the pulse voltage output of the inductance larrangement 90 to the rectier 81 is one of aiding or opposing the pulse input from transformer terminal O depending upon the polarity of the inductance arrangement 90 output. When it is positive, the effect is opposition, the pulse output of arrangement 90 effectively bucking out a portion of the xed amplitude pulse (also of positive polarity) derived from terminal O. This follows from the fact that the two pulse inputs are applied to oppositely poled electrodes of the rectiiier 81.

In the absence of any pulse input from the inductance arrangement 90, the D.C. output of the rectifier 81 substantially corresponds in magnitude to the amplitude of the pulse input from transformer terminal O. An illustrative value for the pulse voltage level attransformer terminial O is +5200 volts. The D.C. voltage delivered to the focus energizing terminal FT is lessened from a 5200 volt level by the application of a positive polarity pulse from inductance arrangement 90 to the reetier 81 cathode, the degree of lessening corresponding to the amplitude of the positive polarity pulse input to the cathode. Conversely, however, when the polarity of the pulse output of inductance arrangement 90 is negative, the D.C. focus voltage developed at terminal FT exceeds the 5200 volt level by an amount determined by the amplitude of the negative pulse input.

Thus, with the illustrative parameter values, positioning of the core 97 in its reference position, to thereby produce a pulse output at terminal F3 of maximum negative value (illustratively, -720 volts), results in maximum increase of the D.C. focus voltage at terminal FT;

i.e., increase to a maximum focus voltage level of +5920 volts. In contrast, movement of the core 97 to the opposite yadjustment extreme produces a pulse output at ter- -minal F3 of +720 volts, the maximum positive value, which will result in maximum reduction of the D.C. focus voltage at terminal FT; i.e., reduction to a minimum focus voltage level of 4480 volts.

To appreciate the effect of the pulse component induced across the F1-M1 segment of coil 91, it may be noted that, with this coil segment eliminated (i.e., replaced by a simple wire connection from S3 to M1), the D.C. focus voltage adjustment range, for the assumed parameter values, would extend from +4420 volts to +5530 volts. The Fl-Ml segment contribution, in the invention embodiment shown in the drawing, is thus seen to significantly expandthe focusing voltage adjustment range at the high end, at the expense of an accompanying slight range reduction at the low end.

If, for the requirements of a particular receiver arrangement, expansion of the focus voltage adjustment range at the low end is particularly desired (as where other receiver requirements place the transformer tapping point for the fixed pulse input to the -focus rectifier at a level near the high end of a desired focus adjustment range), the invention embodiment illustrated in the drawing may be modified to achieve the purpose. The simple modification is to transpose the input leads to the inductanceldivider section of inductance arrangement 90; that is, the illustrated connection from transformer terminal I to start S1 of winding 90, and the illustrated'connection from transformer terminal L to the start SS of winding 95, are exchanged to provide resultant connections between transformer terminal L and start S1, and between transformer terminal J and start S5.

Despite the indicated transposal of input lead connections, the S1-M1 segment of coil 91 and coil 95 still comprise the two inductance divider elements. However, their relative positions in the divider have been exchanged. Center tap M1 of winding 91 remains as the junction of the two divider sections, and the M1-F1 segment of winding 91 still serves to connect the junction to the middle winding 93, in turn still coupled by capacitor 85 to the rectifier 81 cathode.

i Operation under the altered connection conditions is as follows: The divided pulse voltage variation at M1 is the same as with the connections indicated in the drawing in one aspect in that it is of positive polarity throughout the adjustment range; however, the divided pulse voltage at M1 varies from a maximum value (illustratively, +390 volts) at the reference position to a minimum value (illustratively, +60 volts) ,at the opposite adjustment extreme. It will be seen that such pulse voltage variations at terminal M1 directly represents, in the case of the altered connections, the voltage across the winding segment S1- M1, whereas, in the case of the drawing connections, the pulse voltage variation at terminal M1 represented its complement (i.e., the voltage across coil 9S). The pulse voltage induced across middle winding 93 will, as before, vary from a maximum positive value (illustratively, +390 volts) to a maximum negative value (illustratively, 390 volts) over the adjustment range; however, due to the altered connections, the maximum -positive value will occur at the reference core position, and the maximum negative value will be associated with the opposite adjustment extreme. The altered circuit connections will also have a significant effect on the pulse voltage component induced across the Fl-Ml segment of winding 91; under the new conditions, the polarity of this component will be positive throughout the adjustment range, with a maximum value (illustratively, 390 volts) at the reference core position and a minimum value (illustratively, +60 volts) at the opposite adjustment extreme.

The pulse voltage at the output terminal F3 of the inductance arrangement 90, representing the summation of the three components discussed above, thus will have,

tion, .and a maximum negative value (illustratively, -270 volts) at the opposite adjustment extreme. Comparison with the pulse output variations associated with the drawing connections shows that the polarity condition associated with the reference core position is altered, now being maximum positive rather than maximum negative. More significantly, however, the maximum positive value is no longer matched in magnitude with the maximum negative value, as was the case for the original circuit connections. While the total width of the adjustment range is the same in both cases, it is differently distributed; i.e., with the altered connections, a substantially large portion of the adjustment range is in the positive polarity region. The effect on the DC focus voltage output delivered to terminal FT is that the output can be increased from the voltage level set by the fixed amplitude pulse contribution to only a slight extent (e.g., increased by 270 volts), but it can be decreased from such a voltage level to a very substantial extent (e.g., decreased by as much as 1170 volts).

An example of utility for the modification under discussion is where receiver requirements place the voltage level at the transformer tapping point O at +5600 volts, but the same focus adjustment range (e.g., approximately +4450 volts to +5900 volts) as was previously considered is desired. The focus supply of the drawing, with the indicated alteration of input connections, will satisfy such new conditions, providing, for the illustrative parameter values, a maximum DC focus voltage of +5870 volts (i.e., 270 volts added to 5600 volts) and a minimum focus voltage of +4430 volts (i.e., 5600 volts less 1170 volts).

What is claimed is:

1. An adjustable voltage pulse supply comprising the combination of:

a source of input voltage pulses of relatively fixed amplitude having a pair of output terminals;

a first winding;

a second winding comprising first and second segments; means for connecting said lirst winding and said first segment of said second winding in series between said source output terminals;

a third winding;

a variable amplitude pulse output terminal;

means for connecting said third winding and said second segment of said second winding in series between said variable amplitude pulse output terirnnal and the junction of said first winding and said first segment of said second winding;

and means for adjusting the amplitude of the voltage pulse developed at said variable amplitude pulse output terminal, said adjusting means comprising a common core for said first, second and third windings,

the position of said common core being adjustable between a first adjustment extreme at which the common core extends within said first and third windings but is withdrawn from said second winding, and a second adjustment extreme at which said common core extends within said second and third windings but is withdrawn from said first winding, the adjustment of said core position thereby differentially varying the coupling between said first and third windings and the coupling between said second and thirdl windings.

2. An adjustable voltage pulse supply comprising the combination of:

a source of voltage pulses of a given polarity and of relatively fixed amplitude having a pair of output terminals; p

a pair of coils, one of said pair of coils having a larger inductance value than the other;

means for connecting said other coil in series with a portion only of said one coil between said pair of source output terminals;

l l an additional coil inductively coupled to both of said pair of coils, the coupling between said additional coil and said one coil being eiectively oppositely poled with respect to the coupling between said additional coil and said other coil;

a variable pulse output terminal;

means including said additional coil in series with the remaining portion of said one coil for coupling the junction of said other coil and said first-named portion of said one coil to said variable pulse output terminal;

and means providing said pair of coils and said additional coil with a common adjustably positioned core for varying the amplitude and polarity of the voltage pulse developed at said variable pulse output terminal.

3. In a color television receiver including a color kinescope having a focus electrode, and also including a deflection transformer subject to the periodic appearance of flyback pulses, said transformer having first and second terminals, fiyback pulses appearing at said first terminal with a relatively high amplitude, and flyback pulses appearing at said second terminal with a relatively low amplitude; a focus voltage supply comprising in combination:

a rectifier having an anode and a cathode;

means for coupling said rectifier anode to said first transformer terminal;

a first winding having end terminals and an intermediate tap;

-a second winding having end terminals;

means for connecting one end terminal of said first winding to said second Itransformer terminal;

means for connecting one end terminal of said second winding to said intermediate tap of said first windme;

means for connecting the remaining end terminal of said second winding to a point of reference potential;

a third Winding having end terminals;

means for connecting one end terminal of said third winding to the remaining end terminal of said first winding;

a capacitor coupled between said rectiiier cathode and the remaining end terminal of said third winding;

a direct current conductive connection between said rectifier cathode and said focus electrode;

and a common core for said first, second and third windings, the position of said common core being adjustable between a first adjustment extreme at which the common core extends within said first and third windings but is withdrawn from said second winding, and a second adjustment extreme at which said common core extends within said second `and third windings but is withdrawn from said first windlng.

4. In a color television receiver including a color kinel2 scope having a focus electrode, and also including a deflection transformer subject to the periodic appearance of fiyback pulses; an adjustable focus voltage supply comprising in combination:

a focus rectifier having an anode and a cathode; means coupled to said transformer for applying relatively fixed amplitude yback pulses of a first magnitude to said focus rectifier anode;

an inductance voltage divider having a pair of end terminals and an intermediate terminal, said inductance divider comprising a first inductance device connected between said intermediate terminal and a first one of said end terminals, and a second inductance device connected between said intermediate terminal and a second one of said end terminals;

means coupled to said transformer for applying relatively fixed amplitude fiyback pulses of a second magnitude, smaller than said first magnitude, across the end terminals of said inductance divider;

inductive means effectively inductively coupled to but one of said first and second inductance devices;

a winding inductively coupled to both of said rst and second inductance devices but with mutually opposite poling of the respective couplings;

means for connecting said winding in series with said inductive means between said inductance divider intermediate terminal and said focus rectifier cathode;

a direct current conductive connection between said focus rectifier cathode and said focus electrode;

and means for varying the pulse voltage division effected at said intermediate terminal by said inductance divider whereby the voltage developed across each of said inductance devices is varied, and the voltage 1appearing across said inductive means inductively coupled to but one of said inductance devices is also varied, said last named means simultaneously serving to differentially vary the coupling between said winding and said first inductance device and the oppositely poled coupling between said winding and said second inductance device.

OTHER REFERENCES Vonderschmitt and Annus: Focus Voltage Supply for a Color TV Receiver, RCA TN No. 419, January 1961,

JOHN W. CALDWELL, Acting Primary Examiner.

ROBERT L. GRIFFIN, Examiner.

T. A. GALLAGHER, R. K. ECKERT, JR.,

Assistant Examiners. 

1. AN ADJUSTABLE VOLTAGE PULSE SUPPLY COMPRISING THE COMBINATION OF: A SOURCE OF INPUT VOLTAGE PULSES OF RELATIVELY FIXED AMPLITUDE HAVING A PAIR OF OUTPUT TERMINALS; A FIRST WINDING; A SECOND WINDING COMPRISING FIRST AND SECOND SEGMENTS; MEANS FOR CONNECTING SAID FIRST WINDING AND SAID FIRST SEGMENT OF SAID SECOND WINDING IN SERIES BETWEEN SAID SOURCE OUTPUT TERMINALS; A THIRD WINDING; A VARIABLE AMPLITUDE PULSE OUTPUT TERMINAL; MEANS FOR CONNECTING SAID THIRD WINDING AND SAID SECOND SEGMENT OF SAID SECOND WINDING IN SERIES BETWEEN SAID VARIABLE AMPLITUDE PULSE OUTPUT TERMINAL AND THE JUNCTION OF SAID FIRST WINDING AND SAID FIRST SEGMENT OF SAID SECOND WINDING; AND MEANS FOR ADJUSTING THE AMPLITUDE OF THE VOLTAGE PULSE DEVELOPED AT SAID VARIABLE AMPLITUDE PULSE OUTPUT TERMINAL, SAID ADJUSTING MEANS COMPRISING A COMMON CORE FOR SAID FIRST SECOND AND THIRD WINDINGS, THE POSITION OF SAID COMMON CORE BEING ADJUSTABLE 